# Which colour-blind-safe qualitative palette and sequential colour map have primary sources, and what are the exact Okabe-Ito colours and their stated design rules?

- id: art_01M5MTAKY21A5B3P87DG77BY9A
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T17, T20 · tags: none
- updated: 2026-10-23T16:43:23.934Z
- url: https://veyrul.com/articles/art_01M5MTAKY21A5B3P87DG77BY9A

Okabe and Ito (a primary page by two protanopes) propose an 8-colour qualitative palette with stated selection rules: vermilion rather than red, bluish green rather than green, reddish purple rather than violet, avoiding yellow-green, alternating warm and cool, and adding brightness or saturation differences when two warm or two cool colours are combined. Hex values are not in the page text (the palette is an image), so they were taken from R's source table (a secondary implementation, attributed in a code comment to Okabe and Ito). For continuous data, Crameri et al. 2020 (open access) recommend perceptually uniform, lightness-monotonic maps from a listed set rather than rainbow or red-green maps. Wong 2011 (Nature Methods) full text is paywalled.

Okabe and Ito (a primary page by two protanopes) propose an 8-colour qualitative palette with stated selection rules: vermilion rather than red, bluish green rather than green, reddish purple rather than violet, avoiding yellow-green, alternating warm and cool, and adding brightness or saturation differences when two warm or two cool colours are combined. Hex values are not in the page text (the palette is an image), so they were taken from R's source table (a secondary implementation, attributed in a code comment to Okabe and Ito). For continuous data, Crameri et al. 2020 (open access) recommend perceptually uniform, lightness-monotonic maps from a listed set rather than rainbow or red-green maps. Wong 2011 (Nature Methods) full text is paywalled.

Curator qualifications: Verified the selection rules. Note: the page text gives some RGB/hex values in its guidance (e.g. vermilion #FF2000), so 'hex values are not in the page text' should be narrowed to 'the 8-colour palette chart is an image'. Narrow: the palette chart is an image, but the guidance text carries some RGB/hex values (e.g. vermilion #FF2000).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://web.archive.org/web/20210803155953id_/https://jfly.uni-koeln.de/color/",
      "note": "palette guidance"
    },
    {
      "url": "https://github.com/wch/r-source/blob/c39779accd1a64a5223f0061b451f8e46b0c7186/src/library/grDevices/R/colorstuff.R",
      "note": "palette guidance"
    },
    {
      "url": "https://www.nature.com/articles/s41467-020-19160-7",
      "note": "palette guidance"
    },
    {
      "url": "https://www.nature.com/articles/nmeth.1618",
      "note": "palette guidance"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Okabe and Ito (a primary page by two protanopes) propose an 8-colour qualitative palette with stated selection rules: vermilion rather than red, bluish green rather than green, reddish purple rather than violet, avoiding yellow-green, alternating warm and cool, and adding brightness or saturation differences when two warm or two cool colours are combined. Hex values are not in the page text (the palette is an image), so they were taken from R's source table (a secondary implementation, attributed in a code comment to Okabe and Ito). For continuous data, Crameri et al. 2020 (open access) recommend perceptually uniform, lightness-monotonic maps from a listed set rather than rainbow or red-green maps. Wong 2011 (Nature Methods) full text is paywalled. · locator: palette guidance · source: https://web.archive.org/web/20210803155953id_/https://jfly.uni-koeln.de/color/

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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